1. Field of the Invention
The present invention relates to a method of fixing a polygon mirror used for scanning laser beam in a laser beam printer or a digital copier to a side of a rotating member of a motor and a polygon scanner motor using the fixing method.
2. Description of the Related Art
In an optical system such as a laser beam printer or a digital copier, there is used a polygon scanner motor as means for scanning laser beam. A polygon scanner motor of this kind is constituted by fixing a polygon mirror which is formed as a polygonal member in a shape of a thin plate comprising a material of, for example, aluminum and a side face of which is formed by a light reflecting face having mirror face accuracy of submicron order, to a rotor of a motor and is constituted to scan laser beam by making laser beam impinge to the light reflecting face of the side face of the polygon mirror in a state in which the motor is rotated at high speed.
Therefore, according to the conventional polygon scanner motor of this kind, it is necessary to firmly fix the polygon mirror to a rotor rotatably provided to a shaft of a stator via a bearing. Therefore, conventionally, as a method of fixing the polygon mirror, there are used a method of fixing thereof by an adhering agent, a method of fixing thereof by bringing the polygon mirror into press contact with the rotor by a clamp spring and a method of fixing the polygon mirror by plastically deforming portions of the rotor to thereby fixedly calk to the polygon mirror.
Among the conventional methods, the method of fixing the polygon mirror by an adhering agent, poses a problem that time is taken for curing the adhering agent, a long period of time is taken for reaching predetermined fixing strength and accordingly, assembly cost is increased. Meanwhile, the method of fixing the polygon mirror by using the clamp spring poses a problem that the number of parts is increased and accordingly, the costs are ncreased, further, when the polygon mirror is used at high speed rotation of, for example, 50,000 rpm or more, press force by the clamp spring must be increased considerably and there is produced a deformation causing a drawback in scanning light to the reflecting face of the polygon mirror.
Further, when a flange member of a rotating member is fitted to an attaching hole of a polygon mirror, an outer peripheral edge of the flange member is plastically deformed outwardly to be brought into press contact with an inner peripheral edge of the attaching hole of the polygon mirror to thereby achieve bonding of the rotating member and the polygon mirror as is disclosed in, for example, Japanese Patent Laid-Open No. 230268/1997, there poses a problem that there is operated force in a direction of bringing the polygon mirror into press contact with the rotor by calking, thereby, attitude of the polygon mirror is deviated from required attitude relative to the rotor, rotational balance is deteriorated and emittance of noise is caused.
Further, according to such a calking method, large calking force is needed for fixing the polygon mirror, there is operated force directed in a direction inclined to the polygon mirror at the peripheral edge portion of the attaching hole of the polygon mirror. Accordingly, strain is caused at the light reflecting face formed at the side face of the polygon mirror with great accuracy, its flatness is deteriorated and scanning of laser bream cannot be accomplished with great accuracy. As a result, there poses other problem that quality of scanning is deteriorated.
It is an object of the invention to provide a method of fixing a polygon mirror and a polygon scanner motor capable of resolving the above-described problem in the conventional technology.
In order to resolve the above-described problem according to an aspect of the invention, there is provided a method of fixing a polygon mirror which is a method of fixing the polygon mirror by fitting an attaching hole of the polygon mirror having a reflecting face for scanning light at a side face thereof to a projected portion provided at a rotor of a motor wherein a fitting face end edge of the projected portion is arranged to be opposed to a vicinity of a center in an axial direction of an inner peripheral face of the attaching hole and a portion of the fitting face end edge is subjected to plastic deformation in an outer direction to thereby fix the polygon mirror to the rotor.
The fitting face end edge can be an outer peripheral end edge of a stepped recess portion in a ring-like shape formed at an outer peripheral face of the projected portion.
The polygon mirror and the rotor enable to bond by producing the plastic deformation simultaneously at a plurality of locations at equal angular intervals along the fitting face end edge.
A recess is provided previously at the location of producing the plastic deformation and the plastic deformation enables to produce by bringing a calking jig in press contact with inside of the recess. Further, the portion of producing the plastic deformation is made to be able to correspond to an angle portion of the side face of the polygon mirror.
Further, the polygon mirror and the rotor are constituted by metal materials having linear expansion coefficients substantially equal to each other to thereby enable to prevent a state of bonding the polygon mirror and the rotor from being changed by a change in temperature. The polygon mirror and the rotor can be constituted by the same metal material.
According to another aspect of the invention, there is provided a polygon scanner motor which is a polygon scanner motor constituted by fitting and fixing an attaching hole of a polygon mirror formed with reflecting faces for scanning light at side faces thereof to a projected portion provided at a rotor of a motor wherein the projected portion includes a fitting face end edge opposed to a vicinity of a center in an axial direction of an inner peripheral face of the attaching hole of the polygon mirror and the projected portion is formed with plastically deformed portions bonded with the polygon mirror by pressing the inner peripheral face of the attaching hole to an outer side thereof in a diameter direction at a plurality of locations along the fitting face end edge.
Portions of forming the plastically deformed portions can be provided at equal angular intervals along a peripheral direction of the projected portion.
The fitting face end edge is made to enable to be opposed to the vicinity of the center in the axial direction of the inner peripheral face of the attaching hole by providing a small diameter portion at an upper end of the projected portion.